The correct answer is B. Purchase of machinery on credit.
A cash flow is a movement of money into or out of a business. It can be classified as operating, investing, or financing cash flows. Operating cash flows are the cash flows that result from the day-to-day operations of a business. Investing cash flows are the cash flows that result from the purchase or sale of long-term assets. Financing cash flows are the cash flows that result from the issuance or repayment of debt or equity.
In the case of purchasing machinery on credit, the company is not receiving any cash. Instead, it is incurring a liability. This is not a cash flow.
The other options are all cash flows. Option A, sale of fixed assets, is an example of an operating cash flow. Option C, issue of debentures, is an example of a financing cash flow. Option D, cash from business operations, is a general term that can refer to any type of cash flow.